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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

VARIEGATED, ORANGE AND BUTLER GLACIERS                125
•of OUT 1905 and 1906 pictures, looking across the interior flat to the Variegated ice bulb. As compared with 1905, the front of the glacier where it rises above the interior flat was much higher, steeper, and more irregular; but as compared with 1906 it was both lower and much smoother. The serrated crest and steep glacier front, greatly broken by •crevasses in which clear ice appeared in 1906, had by 1909 slumped into an undulating moraine-covered slope (PL LIT) up which we could easily climb. We cannot tell exactly how much change had taken place, for it was impossible to occupy exactly the same photographic sites as in previous years, owing to slumping of the moraine from which our earlier pictures were taken; but there had certainly been a change amounting to scores of feet. Throughout this ice face it is evident that the morainic veneer is thin,, excepting near the ice base to which much debris has fallen.
The most noteworthy fact with regard to the ice condition here is the evidence that when we observed the Variegated Glacier in August, 1906, it had advanced approximately to its maximum. Not only did the advance not affect the black hornblende moraine on the outer side of the interior flat, but it produced no further effect on the interior flat. Thus in an interval of less than a year an utter transformation of Variegated Glacier occurred, breaking its surface, thickening it, and causing some advance, but not affecting the outer stagnant portion. Since 1906 there had been no notable recession of the broken front, for willows grew right up to the base of the moraine; but recession would hardly be expected here, where moraine was still sliding down the steep front and forming a protecting talus at its base.
The granite gorge visible in 1905 was still covered by the glacier,butmorewater emerged from this portion than in 1906, though not nearly so much as in 1905. Evidently the subglacial drainage was again developing, and we may with safety predict a reoccupation of this area by a large glacial stream. There was no noteworthy difference in other parts of the interior flat and the description of its condition in 1905 and 1906 still applied to it. There was a fair-sized stream from the north side, apparently of about the same size as in previous years, but more water than in 1906 crossed the flat from the ice front and escaped through the gorge in the outer glacier to the sea.
The Outer Alluvial Fan in 1909. In 1909 we again visited the huge alluvial fan of the Orange and Variegated Glaciers, whose alder cover in 1906 was being destroyed by the floods of icy water and gravel that swept down the eastern half of the alluvial fan. The glacial torrent still emerged from the southern margin of the Variegated Glacier, apparently in nearly as great a volume as in 1906, but its course was now shifted to the central and western sides of the alluvial fan. Before its course was shifted, however, ithad accomplished great destruction in the alder-covered zone. There was some alder left, notably a band on the eastern margin of the fan and a V-shaped wedge out toward the middle; but fully hah* the alder cover had been destroyed, and the alluvial fan surface was littered with uprooted alder bushes which had been washed down-stream and become stranded, some of them again taking root in the gravels in which they were embedded. Some of the alder still standing in place was partly buried by a deposit of a foot or more of coarse gravel, and some had been killed by deposit without being uprooted. Since we saw the alder still growing in the midst of the muddy distributaries in August, 1906, the season when the destruction began, and since much alder had been removed before 1909, we assume that the destruction continued throughout the season of 1907 and possibly into 1908; but in 1909, for a time at least, the destruction of the alder here had ceased.